Look around you: from copper electrical wires and steel bridges to aluminum foil, gold jewelry, and oxygen gas we breathe, elements are classified into two broad families — Metals and Non-Metals. Understanding their physical and chemical behavior is the core theme of CBSE Class 10 Chemistry Chapter 3.
This guide covers physical properties and key exceptions, chemical reactions of metals with air, water, and acids, the reactivity series, ionic bonding, extraction of metals from ores (metallurgy), electrolytic refining, and methods of corrosion prevention.
- 1. Physical Properties & Important Exceptions
- 2. Chemical Properties & Reactions of Metals
- 3. The Reactivity (Activity) Series of Metals
- 4. Formation and Properties of Ionic Compounds
- 5. Metallurgy & Extraction of Metals from Ores
- 6. Electrolytic Refining & Anode Mud
- 7. Corrosion & Alloy Compositions
- 8. Solved Board Exam Questions
- 9. Frequently Asked Questions (FAQ)
1. Physical Properties & Important Exceptions
| Property | Metals | Non-Metals |
|---|---|---|
| Physical State | Solids at room temperature (except Mercury) | Solids (Carbon, Sulphur), Liquid (Bromine), Gases (Oxygen, Nitrogen) |
| Lustre (Shine) | Lustrous (metallic shine when polished) | Non-lustrous (dull appearance) |
| Hardness | Hard (high tensile strength) | Generally soft |
| Malleability | Malleable (can be beaten into thin sheets) | Non-malleable (brittle, break into pieces) |
| Ductility | Ductile (can be drawn into thin wires) | Non-ductile |
| Electrical & Thermal Conductivity | Good conductors (Silver is best, Copper second) | Poor conductors (insulators) |
| Density & Melting Point | High density and high melting points | Low density and low melting points |
| Sonorosity | Sonorous (produce ringing sound when struck) | Non-sonorous |
⚠️ Crucial Exceptions (Must-Know for CBSE Exams!)
2. Chemical Properties & Reactions of Metals
Metal + Oxygen → Metal Oxide
2Mg(s) + O₂(g) → 2MgO(s) [White Powder] 4Al(s) + 3O₂(g) → 2Al₂O₃(s) Amphoteric Oxides: Metal oxides that react with BOTH acids and bases to produce salt and water are called amphoteric oxides. Examples: Al₂O₃ and ZnO.
Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O | Al₂O₃ + 2NaOH → 2NaAlO₂ [Sodium Aluminate] + H₂O
• Potassium & Sodium (Cold Water): React violently; H₂ gas catches fire immediately.
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)↑ + Heat • Calcium (Cold Water): Less violent; Ca floats because bubbles of H₂ stick to its surface.
• Magnesium (Hot Water): Does not react with cold water; reacts with hot water to form Mg(OH)₂ and floats.
• Aluminium, Iron, Zinc (Steam Only): Do not react with cold or hot water; react ONLY with steam.
2Al(s) + 3H₂O(g) [Steam] → Al₂O₃(s) + 3H₂(g)↑ 3Fe(s) + 4H₂O(g) [Steam] → Fe₃O₄(s) + 4H₂(g)↑ • Lead, Copper, Silver, Gold: Do NOT react with water or steam at all.
Fe(s) + 2HCl(aq) → FeCl₂(aq) + H₂(g)↑ Why Hydrogen is NOT evolved with Nitric Acid (HNO₃):
HNO₃ is a strong oxidizing agent. It oxidizes H₂ gas produced into water (H₂O) and itself gets reduced to nitrogen oxides (NO₂, NO, N₂O). Exception: Magnesium (Mg) and Manganese (Mn) react with VERY dilute HNO₃ to evolve H₂ gas.
3. The Reactivity (Activity) Series of Metals
The Reactivity Series is an arrangement of metals in decreasing order of their chemical reactivity.
| Metal Name | Symbol | Reactivity Category | Extraction Technique |
|---|---|---|---|
| Potassium | K | HIGHLY REACTIVE (Top of Series) | Electrolytic Reduction of molten chloride / oxide ores |
| Sodium | Na | ||
| Calcium | Ca | ||
| Magnesium | Mg | ||
| Aluminium | Al | ||
| Zinc | Zn | MODERATELY REACTIVE (Middle of Series) | Reduction using Carbon (Coke) / Thermite Reduction after Roasting/Calcination |
| Iron | Fe | ||
| Lead | Pb | ||
| [Hydrogen] | [H] | ||
| Copper | Cu | LEAST REACTIVE (Bottom of Series) | Thermal Reduction (heating alone in air) or native state |
| Mercury | Hg | ||
| Silver | Ag | ||
| Gold | Au |
4. Formation and Properties of Ionic Compounds
An ionic compound is formed by the complete transfer of one or more valence electrons from a metal atom (which forms a cation) to a non-metal atom (which forms an anion).
Example: Formation of Sodium Chloride (NaCl)
Na (2,8,1) → Na⁺ (2,8) + 1e¯
Cl (2,8,7) + 1e¯ → Cl¯ (2,8,8)
Electrostatic attraction binds Na⁺ and Cl¯ into a 3D crystalline lattice of NaCl.
Key Properties of Ionic Compounds:
- Physical Nature & Hardness: Hard, crystalline solids due to strong electrostatic forces of attraction between positive and negative ions. Brittle under pressure.
- High Melting & Boiling Points: A large amount of thermal energy is required to break strong inter-ionic bonds. (e.g., NaCl MP = 1074 K).
- Solubility: Generally soluble in polar solvents like water; insoluble in non-polar organic solvents (kerosene, petrol, benzene).
- Electrical Conductivity: Do NOT conduct electricity in the solid state (ions fixed in lattice). Conduct electricity in molten state or aqueous solution where ions are free to move.
5. Metallurgy & Extraction of Metals from Ores
Ore: A mineral from which a metal can be extracted conveniently and profitably.
Gangue: Unwanted earthy impurities (sand, clay, soil) associated with mined ore.
Cinnabar (HgS):
2HgS + 3O₂ → 2HgO + 2SO₂
2HgO + Heat → 2Hg + O₂
2ZnS + 3O₂ → 2ZnO + 2SO₂
Calcination: Heating carbonate ores in limited air.
ZnCO₃ → ZnO + CO₂
ZnO is then reduced with Carbon: ZnO + C → Zn + CO.
Extracted by electrolysis of molten chlorides/oxides.
At Cathode (-): Na⁺ + e¯ → Na(s)
At Anode (+): 2Cl¯ → Cl₂(g) + 2e¯
Thermite Process: Highly exothermic reaction where active metal (like Aluminium) reduces metal oxide. The heat released melts the metal produced. Used to join railway tracks!
Fe₂O₃(s) + 2Al(s) → 2Fe(l) [Molten Iron] + Al₂O₃(s) + Heat
6. Electrolytic Refining & Anode Mud
Impurities present in crude metals are removed by Electrolytic Refining (most widely used for Copper, Zinc, Tin, Nickel, Silver, Gold).
- Anode (+): Thick block of Impure Copper metal
- Cathode (-): Thin strip of Pure Copper metal
- Electrolyte: Acidified Copper Sulphate (CuSO₄ + H₂SO₄) solution
On passing current, pure copper from the anode dissolves into electrolyte and deposits on cathode. Soluble impurities go into solution, while insoluble impurities settle at the bottom of the anode as Anode Mud (contains valuable metals like Ag, Au, Pt!).
7. Corrosion & Alloy Compositions
Methods of Preventing Corrosion:
- Galvanisation: Coating iron/steel with a thin protective layer of Zinc (Zn). Protects even if zinc coating is scratched (sacrificial protection).
- Anodising: Process of forming a thick protective oxide layer on Aluminium by electrolysis using dilute H₂SO₄.
- Alloying: Homogeneous mixture of two or more metals (or a metal and a non-metal) to enhance strength, hardness, and corrosion resistance.
| Alloy Name | Composition (Constituents) | Properties & Industrial Uses |
|---|---|---|
| Stainless Steel | Iron (Fe) + Chromium (Cr) + Nickel (Ni) + Carbon (C) | Hard, does not rust; surgical tools, utensils, food processing |
| Brass | Copper (Cu) + Zinc (Zn) | Malleable, decorative items, musical instruments, electrical fittings |
| Bronze | Copper (Cu) + Tin (Sn) | Corrosion resistant; statues, medals, coins, ship propellers |
| Solder | Lead (Pb) + Tin (Sn) | Low melting point; welding electrical wires together |
| Amalgam | Mercury (Hg) + another metal (e.g., Dental Amalgam) | Dental fillings, chemical reduction catalysts |
8. Solved Board Exam Questions
Equation: 2ZnS(s) + 3O₂(g) → 2ZnO(s) + 2SO₂(g)
Calcination: Process of heating a carbonate ore strongly in the absence or limited supply of air to convert it into metal oxide.
Equation: ZnCO₃(s) → ZnO(s) + CO₂(g)
Two examples: Aluminium oxide (Al₂O₃) and Zinc oxide (ZnO).
Reaction with Acid: Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O
Reaction with Base: Al₂O₃ + 2NaOH → 2NaAlO₂ (Sodium Aluminate) + H₂O
(a) Platinum, gold, and silver are used to make jewelry.
(b) Sodium and potassium are stored under kerosene oil.
(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
(b) Sodium and potassium are highly reactive alkali metals. They react explosively with atmospheric oxygen and moisture, catching fire. Kerosene prevents air/water contact.
(c) Aluminium reacts with atmospheric oxygen to form a thin, tough, non-porous protective layer of aluminium oxide (Al₂O₃) on its surface that prevents further corrosion.
Na• + ••Cl••: → [Na]⁺ [••Cl••:]¯ → NaCl
MgO: Mg (2,8,2) loses 2e¯ to form Mg²⁺ (2,8). O (2,6) gains 2e¯ to form O²¯ (2,8).
Mg:• + ••O•• → [Mg]²⁺ [••O••:]²¯ → MgO
Equation: Fe₂O₃(s) + 2Al(s) → 2Fe(l) + Al₂O₃(s) + Heat
Application: Used in thermite welding to join broken railway tracks and cracked machine frames.
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9. Frequently Asked Questions (FAQ)
Metals are electropositive elements that readily lose valence electrons to form cations. They are hard, malleable, ductile, sonorous, good conductors of heat and electricity, and form basic oxides (e.g., Na, Fe, Cu).
Non-metals are electronegative elements that gain or share electrons. They are brittle, non-malleable, poor conductors (insulators), and form acidic or neutral oxides (e.g., C, S, O₂, N₂).
The reactivity series is a list of metals arranged in decreasing order of their chemical reactivity: K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au. Metals placed above hydrogen displace H₂ gas from dilute acids, whereas metals placed below hydrogen do not react with dilute acids.
Roasting is the process of heating sulphide ores strongly in the presence of excess air to form metal oxides (e.g., 2ZnS + 3O₂ → 2ZnO + 2SO₂).
Calcination is the process of heating carbonate ores strongly in the absence or limited supply of air to form metal oxides (e.g., ZnCO₃ → ZnO + CO₂).
Ionic compounds consist of positive and negative ions bound together by strong electrostatic forces of attraction in a 3D crystal lattice. Breaking these strong bonds requires a large amount of thermal energy, resulting in high melting points.
In the solid state, ions are fixed in position and cannot move, so they do not conduct electricity. In molten state or aqueous solution, the crystal lattice breaks apart, allowing ions to move freely and carry electrical current.
Galvanisation is the method of protecting iron and steel from rusting by applying a thin coating of molten **Zinc (Zn)**. Zinc acts as a physical barrier against moisture and oxygen. Even if the zinc coating is scratched, zinc corrodes preferentially because it is more reactive than iron (sacrificial protection).
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